The present invention relates to a digital signal transmission system. More particularly, it relates to a data synchronizing system.
The conventional data synchronizing system in the serial transmission system will be illustrated by a simple example.
FIG. 1 shows one embodiment of a data stream. FIG. 2 shows a diagram of a simple block codification. FIG. 3 shows a diagram of a transmission format. The reference numeral(1) designates a data stream; (11) designates a message; (12) designates a vertical parity; (13) designates a horizontal parity;(2) designates a transmission format; (20) designates a frame synchronous code; (21) designates a first frame data; (22) designates a second frame data;(23) designates a third frame data; (24) designates a fourth frame data; and (25) designates a block synchronous code. The following case is considered. The data stream is made of continuous messages (11) having 12 bits shown in FIG. 1 and the message is arranged into 3 rows 4 columns matrlx shown in FIG. 2 and vertical and horizontal parities are given to arrange 4 by 5 matrix and each row is transmitted as one frame. In order to determine which is the first bit of the frame, each frame synchronous code (20)is given. The matrix is considered as one block A block synchronous code (25) for synchronizing the blocks should be given. This is a simple example. In usual, coded trains having block structure are transmitted, a block synchronous code (25) should be given beside the frame synchronous codes (20). The code length of the block synchronous code (25) must be long so as to select without disturbance of the frame correlation of the frame synchronous code (20) whereby the redundancy of codes is high to decrease the transmission efficiency.